Synthesis and Characterization of TiO₂−MgO Mixed Oxides Prepared by the Sol−Gel Method

Abstract

Titania−magnesia mixed oxides, with magnesia concentrations between 10 and 90 wt %, were prepared by using the sol−gel method with titanium n-butoxide and magnesium ethoxide as precursors. The mixed oxides were characterized with X-ray powder diffraction, BET nitrogen adsorption isotherms, electron spin resonance (ESR), and by testing their catalytic activity for 2-propanol and 2-butanol dehydration. Samples contained periclase, anatase, karooite (MgTi2O5), geikielite (MgTiO3), and qandilite (Mg2TiO4). The BET specific surface area varied with magnesia concentration; the samples with 50 wt % MgO had the highest area, 211 m2/g. Samples had paramagnetic centers that produced complex ESR spectra when many crystalline phases coexisted. For 2-propanol and 2-butanol decomposition, the activity and selectivity patterns of the mixed oxides were substantially different to those observed in pure TiO2 and pure MgO. This singular behavior should be a result of the structural defects created by the substitution of Mg2+ ions by Ti4+ cations in titania lattice, as well as by the interfaces created when several crystalline phases coexisted.